What a 1/5 rating means
On the comedogenic scale, a 1 sits at the safe end of the scale — clogging is unlikely for most people. That places PEG-100 Stearate in the range most people, including many with acne-prone skin, tolerate well.
One thing the number cannot tell you is concentration. Ingredients are listed in descending order, so PEG-100 Stearate near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About PEG-100 Stearate
It is an emulsifier, the ingredient that keeps a product's oil and water phases from separating. A very common co-emulsifier (usually paired with glyceryl stearate) that is low-risk at 1/5, though a fatty-acid ester.
On a label it can read as Peg-100 Stearate, Peg 100 Stearate — worth knowing when you scan an ingredient deck.
PEG-100 Stearate in makeup and skincare
It quietly stabilises most cream foundations, lotions, and moisturisers. Its irritancy is rated separately at 0/5, which is low.
If you deal with fungal acne (malassezia folliculitis) rather than ordinary clogged pores, note that PEG-100 Stearate is among the fatty-acid or ester-type ingredients that community sources commonly avoid — a separate concern from its comedogenic score, and one with weaker evidence behind it.